Machines for the forming, filling and sealing of packages made from a continuous web or film of material are well known in the art. The machines comprise a supply of packaging film, a former and edge sealer for forming the film into a continuous hollow tube and reciprocating sealing and cutting jaws for sealing and cutting the tube into a consecutive series of filled packages. The machines have become increasingly popular in the packaging field due to their simplicity and speed of operation. Difficulties arise, however, when the machines are used to package bulky, lightweight materials, such as potato chips, that bunch and bridge so as to resist settling by gravity alone.
Initially in the art this problem was addressed simply by providing a length of packaging film sufficient to hold the greatest volume that the desired weight of product could assume. Such packaging is unsatisfactory, however, since the product settles during subsequent handling. The settling results in packages having the undesirable appearance of being improperly filled even when containing the proper net weight of product. Disadvantageously, the partially filled appearance of the packages promotes a negative consumer reaction adversely affecting product sales. A further concern to the manufacturer is the required additional packaging film needed for each package of a longer length. The use of this additional packaging film adds substantially to the costs to the manufacturer.
Recognizing these shortcomings, two separate approaches have developed in the art for solving this problem. The first approach involves the provision of vibrating clamps to the packaging machine. As shown in U.S. Pat. No. 3,684,254 to Henry, owned by the assignee of the present invention, the vibrating clamps are closed to engage the packaging film following the product filling cycle. The vibratory motion of the clamps is then imparted to the packaging film to settle the product in the package.
The second approach, which can be used separately or in conjunction with the first, involves the provision of stripper jaws to the packaging machine. The stripper jaws function to mechanically force or strip the product in the packaging film down into the package being formed. As shown in U.S. Pat. Nos. 2,915,866 to Bartlo and 3,027,695 to Leasure, opposing stripper jaws mounted on the sealing jaws are moved into contacting engagement around the packaging film so as to flatten the walls of the packaging film tube together. The stripper jaws or the packaging film is then moved relative to the sealing jaws of the packaging machine so that the product is stripped downward. This provides a packaging film sealing zone free of product adjacent the sealing jaws. The sealing jaws are then brought into engagement across the film to seal the film containing the settled product into a package.
The Bartlo stripper jaws are specifically adapted to be mounted directly above the sealing jaws of the packaging machine. Consequently, there is no provision for product holding jaws. Further, even if holding jaws were provided, they could not possibly be positioned adjacent the sealing jaws due to the positioning of the stripper jaws above the sealing jaws. Without holding jaws positioned adjacent the stripper jaws, the speed of a packaging operation is limited as filling of the next package cannot take place until the stripping and sealing of the present package is completed.
In addition, there is no provision for vents in the Bartlo stripper rods to allow the passage of air from the bag during stripping action. Therefore, as the bag is stripped, air pressure builds in the bag, possibly resulting in the longitudinal or bottom sealed edges of the bag bursting.
The combined sealing and stripper jaw assembly of Bartlo is of excessive overall height increasing the overall packaging machine height requirements. Proper stripping operation of the Bartlo mechanism requires the sealing jaws to travel over a longer path during each packaging machine cycle. This is due to the mounting of the stripper jaws so as to extend inwardly from the sealing jaws toward the packaging film. This additional path length for proper operation further reduces overall packaging machine speed and efficiency. In addition, the excessive weight of the reciprocating Bartlo stripper/sealing jaws adversely affects the smooth operation of the packaging machine.
In Leasure, stripper plates are brought together in operative position so as to engage the packaging film. The reciprocating former then pulls the film upward in reverse direction through the stripper plates. The stripper plates serve to flatten the film and force any product down into the package to provide a clear sealing area.
The requirement of a reciprocating former as in Leasure greatly reduces packaging machine speed of operation, smoothness and efficiency. In addition, the stripper plates of Leasure are shown spaced at all times below the sealing jaws. This leads to a waste of packaging film. That is, the packaging film provided between the stripper plates and the sealing jaws in each bag is not stripped so that each stripping cycle must start higher than would otherwise be required. Elimination of this waste packaging material in each package (approximately 3/8" on an average size bag) produced by just one packaging machine during a single day or operation leads to a large savings in manufacturing costs.
From the above, it is clear that a need exists for an improved mechanism for stripping bulky, lightweight product from the packaging film sealing zone in a form, fill and seal packaging machine.